1. Field of the Invention
This invention relates to a planar antenna and particularly to an arrayed planar antenna where a plurality of radiating elements are arrayed on a dielectric plate.
2. Description of the Related Art
Planar antennas used for micro wave, millimetric-wave etc. are composed of an earthing conductive plate, a feeding substrate where a radiating element is formed on a dielectric plate, a band adjusting element plate where a band adjusting conductive element is formed on a dielectric plate, an unnecessary radiation suppressing conductive plate where a slot for suppressing unnecessary radiation is formed on a dielectric plate. The components above are stacked in this order on the earthing conductive plate. The radiating element is of conductive part to radiate a radio wave by resonating at the half wavelength of transmission radio frequency signal.
FIG. 1 is a plan view showing the arrangement of radiating elements of a radiating element plate 1A in a conventional arrayed planar antenna. As shown in FIG. 1, the radiating elements 1 each are arrayed at an equal interval L1 on a dielectric plate 5 of the radiating element plate 1A.
In the conventional planar antennas, the dielectric plate is costly since its quality has to be high in order to reduce the loss thereby enhancing the efficiency. Also, the productivity of the conventional planar antennas is low since it is difficult to accurately position the dielectric plates, radiating elements etc. when they are stacked to fabricate the planar antenna.
On the other hand, it is desired that one planar antenna can be adapted to several frequency bands since radio communications using several frequency bands are recently becoming popular.
Furthermore, although in the conventional planar antennas a plurality of radiating elements are, as shown in FIG. 1, arrayed connected in parallel by a feeder wiring to enhance the output of the antenna, there are problems that the radiating elements influence one another or the feeder wiring influences the radiating element, thereby causing an unnecessary radiation, a reduction in directivity etc.